Hydraulic structures can be a promising place for tidal energy extraction due to the high flow velocities, easy access to the power grid and easy access for maintenance. However, quantification of the impacts of a tidal power plant in a hydraulic structure is not straight forward. In 2015 a pilot plant consisting of an array of five Tocardo tidal turbines was installed in the Eastern Scheldt Storm Surge Barrier in the Netherlands. This pilot was accompanied by monitoring studies to verify that the operation of the plant had no adverse impact on the barrier and its surroundings. This paper presents the assessment of the hydraulic impact of the tidal power plant in the storm surge barrier based on an analysis of water level and current measurements, combined with numerical modeling and followed by an assessment of the environmental impact with emphasis on the effects on the intertidal areas in the estuary. This validation approach by a pilot plant is imperative to understand the interaction between tidal turbines and the hydraulic structure on the local scale. This understanding gives extra credibility to the predictions of the extrapolated large-scale and large array assessments which will always be fully numerical.@en